Millions of people in the United States could be forced to abandon their homes if planet-warming emissions continue unabated through 2100, pushing global sea levels up by more than 14 feet (4.2 metres), researchers said.
In the United States, between 20 and 31 million people are living on land that would be submerged by rising oceans without aggressive cuts to greenhouse gas emissions, according to a study published on Monday in the Proceedings of the National Academy of Sciences.
That scenario could occur if global average temperatures rise by 3.3 degrees Celsius (5.9 degrees Fahrenheit) from pre-industrial levels by the end of the century, said the study's lead author, Benjamin Strauss.
Scientists fear ice sheets in Antarctica and other regions will melt as global temperatures increase, leading to major rises in sea levels.
"I would avoid buying property in South Florida in particular," Strauss told the Thomson Reuters Foundation.
Coastal California, New York and other cities on the U.S. east coast would also be hit hard by rising seas if carbon emissions are not cut drastically, he said.
To substantially blunt the threat, emissions reductions would have to be bigger than those pledged by the United States and more than 145 other countries as part of a new U.N. deal to tackle climate change due to be agreed in December.
An independent, science-based analysis released this month by Climate Action Tracker, said those plans, if implemented, would keep global warming to 2.7 degrees Celsius, higher than an internationally agreed limit of 2 degrees.
"Our actions today determine sea-level rise tomorrow," said Strauss, from the scientific group Climate Central, in a statement.
"We can act ... or we can delay and leave a legacy of irreversible rising seas that threaten to destroy some of our nation's most iconic cities."
The study did not look at the impacts of rising sea levels on cities in other countries.
To hammer home the message in the United States, where some politicians and voters remain sceptical about human-induced climate change, researchers built a map allowing residents to type in their postal code to see if their city is projected to be underwater by 2100 (choices.climatecentral.org).
(Thomson Reuters Foundation; Reporting By Chris Arsenault; Editing by Megan Rowling)